Previously the HTML writer was exceptional in not being
sensitive to the `--wrap` option. With this change `--wrap`
now works for HTML. The default (as with other formats) is
automatic wrapping to 72 columns.
A new internal module, T.P.Writers.Blaze, exports `layoutMarkup`.
This converts a blaze Html structure into a doclayout Doc Text.
In addition, we now add a line break between an `img` tag
and the associated `figcaption`.
Note: Output is never wrapped in `writeHtmlStringForEPUB`.
This accords with previous behavior since previously the HTML
writer was insensitive to `--wrap` settings. There's no real
need to wrap HTML inside a zipped container.
Note that the contents of script, textarea, and pre tags are
always laid out with the `flush` combinator, so that unwanted
spaces won't be introduced if these occur in an indented context
in a template.
Closes#7764.
Screen readers read an image's `alt` attribute and the figure caption,
both of which come from the same source in pandoc. The figure caption is
hidden from screen readers with the `aria-hidden` attribute. This
improves accessibility.
For HTML4, where `aria-hidden` is not allowed, pandoc still uses an
empty `alt` attribute to avoid duplicate contents.
Closes: #6491
